Double‐ridged conical horn antenna for wideband applications

In this article, the design and analysis of a double‐ridged conical horn antenna with high gain and low cross polarization for wideband applications is presented. Double‐ridged pyramidal horn antennas have been investigated in many references. There are no papers in the literature which are devoted to design and analysis of double‐ridged conical horn antenna. The designed antenna has a voltage standing wave ratio (VSWR) less than 2.1 for the frequency range of 8–18 GHz. Moreover, the proposed antenna exhibits extremely low cross polarization, low side lobe level, high gain, and stable far‐field radiation characteristics in the entire operating bandwidth. A new technique for synthesizing of the horn flare section is introduced. A coaxial line to circular double‐ridged waveguide transition is introduced for coaxial feeding of the designed antenna. The proposed antenna is simulated with commercially available packages such as CST microwave studio and Ansoft HFSS in the operating frequency range. Simulation results for the VSWR, radiation patterns, and gain of the designed antenna over the frequency band 8–18 GHz are presented and discussed. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Quad‐ridged conical horn antenna for wideband applications

This article presents a quad‐ridged conical horn antenna with high gain and low side lobe level for broadband applications. To the best of authors' knowledge, the proposed structure presented in this article is completely new. The designed antenna introduces a low VSWR, which is lower than 2.2 for the frequency range of 8–18 GHz, and simultaneously achieves high gain as well as dual‐polarizations with high isolation between the corresponding excitations. The common impedance exponential tapering is used at the flare section of the horn, and a coax to waveguide transition, namely quadruple‐ridged circular waveguide, with a conical cavity is used to improve the VSWR. The proposed antenna structure is designed and simulated by two well established packages, namely the CST microwave studio and the Ansoft HFSS, showing there is a close agreement between the results obtained by the aforementioned softwares. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Design of conical DRH antennas for K and Ka frequency bands

Two conical double‐ridged horn (DRH) antennas for K and Ka frequency bands are presented. Detailed simulation and experimental investigations are conducted to understand their behaviors and optimize for broadband operation. The designed antennas were fabricated with 0.01 mm accuracy and satisfactory agreement of computer simulations and experimental results was obtained. The designed conical DRH antennas have voltage standing wave ratio (VSWR) less than 2.1 and 2.2 for the frequency ranges of 18–26.5 GHz (K band) and 26.5–40 GHz (Ka band), respectively. Meanwhile, the proposed antennas exhibit low cross‐polarization, low sidelobe level, and simultaneously achieve slant polarization as well as symmetrical radiation patterns in the entire operating bandwidth. An exponential impedance tapering is used at the flare section of the horns. Moreover, a new cavity back with a conical structure is used to improve the VSWR. Numerous simulations via Ansoft HFSS and CST Microwave Studio CAD tools have been made to optimize the VSWR performance of the designed antennas. Simulation results show that the VSWR of the proposed antennas is sensitive to the probe spacing from the ridge edge and the cavity back structure. The designed conical DRH antennas are most suitable as a feed for the reflectors of radar systems and satellite applications. Results for VSWR, far‐field E‐plane and H‐plane radiation patterns, and gain of the designed antennas are presented and discussed. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2011.     

Pattern squint elimination for quad‐ridged conical and pyramidal horn antennas using bended probes

This article describes a new technique for pattern squint elimination of quad‐ridged conical and pyramidal horn antennas by introducing bended coaxial probes. Because of the phase difference and mutual coupling between vertical and horizontal polarizations, the radiation patterns of the conventional quad‐ridged conical and pyramidal horn antennas squint over a wide bandwidth. The proposed technique substantially reduces the phase difference and coupling between the two probes, so a significant improvement in the radiation patterns over the frequency band of 8–18 GHz can be achieved. The designed modified horn antennas are most suitable as a feed element in reflectors of radar systems and EMC applications. The proposed modified antennas have a voltage standing wave ratio (VSWR) less than 2.2 for the frequency range of 8–18 GHz. Moreover, the proposed antennas exhibit high gain, dual‐polarization performance, good isolation, low SLL, low back lobe, low cross polarization, and satisfactory far‐field radiation characteristics for the entire frequency band. © 2009 Wiley Periodicals, Inc. Int J RF and Microwave CAE 2010.     

A Q‐band compact high‐performance double‐ridged orthomode transducer

In this article, a Q‐band compact waveguide orthomode transducer (OMT) based on a stepped double‐ridged waveguide is presented. By using a symmetrical structure, good output return losses of above 20 dB are obtained from 35 to 50 GHz. In particular, the measured insertion losses are as low as 0.15 to 0.4 dB over the entire band for both polarization channels with an improved assembly configuration. The measured cross‐polarization levels are well below ?37 dB, while the circular‐polarized output port isolation is less than ?20 dB combined with a feed horn and a differential phase shifter. The developed OMTs have been used in a Q‐band two‐beam cryogenic receiver on the Tianma Radio Telescope, contributing only 1 to 2 K noise at an operating temperature around 20 K.     

Radiation pattern and properties of double‐flared diagonal horn antenna

This article is concerned with analytical model for radiation pattern of a new double‐flared diagonal horn antenna using “plane wave spectra technique for 3D fields”. The double‐flared diagonal horn antenna is accomplished by adding one more set of flares in E‐ and H‐planes with equal flare angles into conventional diagonal horn. The copolarized and cross‐polarized radiation patterns in E‐, H‐, and D‐planes have been computed utilizing the analytical model and reported in the article. The parametric studies on peak cross‐polarization level have carried out. The radiation performance of double‐flared and conventional diagonal horns for same length and aperture size are also compared. It is investigated that double‐flared diagonal horn antenna posses better peak cross‐polarization level (≈?16.5 dB) in D‐plane (±45° plane) in comparison of conventional diagonal horn (≈?15.5 dB) at design frequency and retains almost circularly symmetric radiating beam at lower values of elevation angles. Also, double‐flared diagonal horn has better matches with free‐space and has slightly lower gain (≤0.5 dB) in comparison of conventional diagonal horn. The work presented here can provide useful design guidelines for development of prototypes of double‐flared diagonal horn, which may find potential application in satellite communication and imaging applications etc. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2009.     

Improved design procedure for double‐ridged waveguides

This article presents a novel methodology for designing double‐ridged waveguides by numerically optimizing their geometric shape such that they sustain the two prescribed lowest order modes. The field solution to the problem is obtained by using the finite element method. The performance of the microgenetic algorithm and the quasi‐Newton methods is studied for carrying out geometry optimization. This generalized formulation is capable of handling inhomogeneous material fillings in the guide, and computational results are presented to demonstrate the versatility of the proposed technique. © 2002 Wiley Periodicals, Inc. Int J RF and Microwave CAE 12, 530–539, 2002. Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mmce.10053     

Microwave conical horn antenna with dual circular polarization—Close‐form design equations

In this article, we have proposed the closed form expressions for the optimized dimensions of different parts of the metallic stepped septum in a circular waveguide. Using these relations, a dual circularly polarized (CP) horn can be realized with good AR bandwidth, impedance bandwidth, and interport isolation. The relations are generalized for application at all frequency bands. Using these relations, horns have been designed and simulated at different frequency bands. Prototypes have been fabricated at some frequency bands and are experimentally validated. This design yields impedance bandwidth (S₁₁ ≤ ?10 dB) of about 18%, AR bandwidth more than 15%, and interport isolation about 24 dB at the band center. Experimental data for the Ka‐band prototype are provided in detail. At the design frequency, the measured axial rations are <1 dB revealing cross‐polar discrimination over 25 dB.     

Design of a 16‐beam pattern‐reconfigurable antenna for vehicular environment

This article presents the design of a multipattern antenna with pattern switching for vehicular communications. The proposed antenna has four triangular patches integrated onto a split square ring (SR) resonator to operate at two distinct frequencies, viz. 2.4 and 3.5 GHz. The proposed antenna is designed with a view to enhancing the link reliability of Wireless Local Area Network (WLAN), WiMax, and vehicle to vehicle communication frequencies. Each triangular patch is separately excited using a microstrip line feed to enable beam steering. The ground plane of the antenna is embedded with two SR slots to improve the bandwidth and radiation performance. Further gain enhancement is achieved by loading the antenna with a plane reflector located at a distance of 20 mm from the antenna's ground surface. In reality, this reflector is realized using the vehicle's roof which provides gain enhancement up to 5.2 dBi at 2.4 GHz and 4 dBi at 3.5 GHz. By exciting single to multiple ports sequentially 16 different radiation patterns are obtained, which provides high‐gain omnidirectional coverage. The prototype antenna is fabricated and the simulation results are verified using experimental measurements. From the results, it is evident that the proposed antenna is suitable for vehicular communication applications.     

Low‐profile wideband patch antenna using double‐tuned impedance matching

A low‐profile wideband patch antenna utilizing double‐tuned impedance matching technology is investigated in this paper. To extend the operation bandwidth of the antenna, the step‐folded probe is used here to realize the double‐tuned impedance matching. Using equivalent circuit theory, the working principle of the antenna is analyzed and discussed. The full‐wave simulation is carried out to optimize the design while the prototype of the antenna is fabricated and measured. Good agreement between the simulation and measurement can be observed. The measured results show that the antenna has a height of 0.12λ_L (λ_L is the free space wavelength corresponding to lowest frequency) and the ?10 dB impedance bandwidth can cover 1.60‐2.83 GHz (55.5%). The low profile and wide operation bandwidth of the antenna make it a good candidate for wideband wireless communication systems.     

Symmetrical double‐comb multi‐slotted large bandwidth antenna for intelligent transportation systems

This article presents a novel compact circularly polarized multi‐slotted large bandwidth antenna for intelligent transportation system (ITS). The proposed antenna has a rectangular shaped multi‐slotted patch on upper side and a partial ground plane with multiple slots on lower side. The designed prototype antenna works from 22 to 29 GHz and is therefore applicable for ITS and weather forecasting applications. The design structure is distinct in terms of a low profile as well as simple structure, which is advantageous in mass production. Moreover, the multiple slots design antenna provides enhanced bandwidth. The axial ratio shows that the proposed antenna's behavior is circularly polarized with a compact size of 30 × 20 mm². The measured reflection coefficient, gain, and the radiation pattern are consistent with simulated results. The proposed antenna has a reflection coefficient below ?20 dB and maximum gain of ~5 dBi at 24 GHz (ITS band).     

Double U‐slots patch antenna for tri‐band wireless systems

A compact microstrip patch antenna with two U‐slots shape is presented. Detailed simulation and experimental investigation are conducted to understand the behavior of the two U‐slots. The proposed antenna generates three resonant frequencies at 2.7, 3.3, and 5.3 GHz. It can, therefore, be used in Worldwide Interoperability for Microwave Access compliant communication equipment. The proposed antenna has two U‐slot shaped and two bridge elements to connect both shapes together to adapt the structure to the desired interest operating frequency. A comprehensive parametric study has been applied to understand the effect of each U‐slot on the antenna's performance. Moreover, the current distribution for the three bands is investigated to give further understanding of the antenna behavior. The proposed antenna is verified experimentally and the simulated and measured results are in good agreement. © 2010 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2010.     

A 60‐GHz on‐chip slot‐array antenna in integrated‐passive‐device technology for antenna‐in‐package applications

A new millimeter‐wave antenna structure on a low‐cost, production platform integrated passive device technology is presented. The antenna consists of a 2‐by‐1 array of slot antennas at 60 GHz. An in‐house developed on‐chip antenna measurement setup was used to characterize the fabricated antenna. The measurement results show an antenna gain of more than 5 dBi with a return loss of 18 dB at 60 GHz. The better‐than‐10‐dB impedance bandwidth of the antenna covers the 60‐GHz unlicensed band from 57 to 64 GHz. The 3‐dB beamwidths of the antenna are 105° and 76° at E‐plane and H‐plane at 60 GHz, respectively. The size of the die of the antenna is 2 mm × 4.5 mm. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:155–160, 2014.     

Metamaterial inspired CPW‐fed compact antenna for ultrawide band applications

A small size, planar and co‐planar waveguide fed metamaterial inspired antenna is proposed for ultra‐wideband (UWB) application. The main radiating element consists of three split‐ring resonators (SRR) and placed along one axis. Moreover, coplanar waveguide (CPW)‐fed line along with modified ground plane is used to improve the impedance matching. The physical size of proposed antenna is 25(W) × 22 (L) × 1.6 (H) mm³. The CPW‐fed metamaterial inspired antenna provides bandwidth of 10.4 GHz from 3.1 to 13.5 GHz based on the 3:1 (voltage standing wave ratio [VSWR] <2). Over the range of UWB frequency, peak realized gain varies from 2.5 to 4 dBi. The proposed antenna provides omnidrectional radiation patterns. Further, fidelity factor of the proposed antenna is also calculated and measured. The calculated fidelity factor is suitable for UWB applications. Finally, prototype of the antenna is developed and tested using network analyzer. The simulated and measured results are in good agreement.     

RF MEMS impedance tuners for 6–24 GHz applications

RF MEMS tuners with wide impedance coverage have been developed for 6–24 GHz noise parameter and load‐pull measurement systems. The tuners are based on triple‐, double‐, and single‐stub topologies loaded with switched MEMS capacitors. Several designs are presented, and they use 10–13 switched MEMS capacitors to produce 1024–8192 (2¹⁰–2¹³) different impedances. The measured impedance coverage agrees well with simulations and it is the widest ever measured impedance coverage from any planar tuner to‐date. © 2007 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2007.     

Design of a dual‐polarized omnidirectional antenna for broadband applications

A broadband dual‐polarized omnidirectional antenna is presented. The proposed antenna consists of two parts, an asymmetric biconical antenna and a cylindrical multilayer polarizer. To have an almost perfect omnidirectional radiation pattern in the horizontal plane and the main radiating beam position at around , in the elevation plane, the asymmetric biconical antenna is used. Moreover, to provide dual polarization performance over the 2–18 GHz operational bandwidth, a multilayer polarizer is designed and optimized. Numerous simulations via Ansoft HFSS and CST microwave Studio CAD tools have been made to optimize the radiation pattern, gain, polarization, and the reflection coefficient of the antenna. Simulation results show that the radiation characteristics of the proposed antenna are extremely sensitive to the configuration and dimensional parameters of the multilayer polarizer. The designed antenna was fabricated with high mechanical accuracy and measured. Satisfactory agreement of computer simulations and experimental results was obtained. The main feature that distinguishes this antenna from the previous designs is the ability to provide the omnidirectional radiation pattern with small ripples, dual polarizations performance, and the wide bandwidth simultaneously. Based on these characteristics, the proposed antenna can be useful for broadband communication applications. © 2015 Wiley Periodicals, Inc. Int J RF and Microwave CAE 25:591–600, 2015.     

A 2 × 2 array antenna with circular polarization and conical beam radiation

A circular disk patch antenna loaded with a hemi‐circular slot is initially proposed for achieving circular polarization (CP). To exhibit broad CP bandwidth that can cover the WLAN 2.4 GHz operating band, the patch antenna is fed by an L‐shaped probe. To further attain conical beam radiation with peak gain of ～8 dBic at ±30 degrees theta angle (θ), a 2 × 2 array type is proposed in this study, in which four circular disk patch array elements are arranged in a sequentially rotated fashion via a corporate feed network. Here, desirable 3‐dB axial ratio (AR) bandwidth and 10‐dB impedance bandwidth of ～5% and 21% were measured. © 2013 Wiley Periodicals, Inc. Int J RF and Microwave CAE 24:223–228, 2014.     

Compact slotline fed enhanced gain dipole antenna for 5.2 GHz/5.8‐GHz applications

A high‐efficiency and high‐gain slotline fed directive dipole antenna is developed for microwave applications. The antenna offers an average gain of 7.9 dBi with a front to back ratio better than 20 dB and a cross polar level better than ?20 dB. Design equations of the antenna are developed and validated on different substrates. The simulation and experimental results show that the proposed antenna exhibits high gain and robust radiation patterns in the entire frequency band. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

Quasi‐corrugated substrate integrated waveguide H‐plane horn antenna with wideband and low‐profile characteristics

A wideband H‐plane horn antenna based on quasi‐corrugated substrate integrated waveguide (SIW) technology with a very low profile is presented in this article. Open‐circuited microstrip stubs are applied to create electric sidewalls of the quasi‐corrugated SIW structure. The quasi‐corrugated SIW H‐plane horn antenna shows high performance and simple structure. A specify‐shaped horn aperture is utilized, so that the poor impedance matching owing to the structure restriction can be smoothened. The structure is simulated by ANSYS HFSS and a prototype is fabricated. The measured results match well with the simulated ones. An enhanced impedance bandwidth ranging from 5.3 GHz to 19 GHz (VSWR < 2.5) is achieved. The presented antenna also brings out stable radiation beam over the same frequency band.     

Parametric study of a UWB parallel‐plate monopole antenna for operation in the 5‐ to 20‐GHz band

A directional ultra‐wideband (UWB) planar antenna is presented in this article. The obtained antenna bandwidth is in the order of 10:1. The directional behavior is gotten by slating a planar monopole antenna with respect to the ground plane. The UWB and directional characteristics of this antenna was obtained by optimizing four parameters: bevelling and slating angles, the size of the matching impedance hole, and the ratio between the height and width of the radiating element. The relatively easy construction of the antenna is one of its main features along with its gain, which goes from 0 to 8.1 dB in the band from 2.6 to 20 GHz. Results obtained by simulation and measurements are in close agreement. © 2008 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2008.